1. Field of the Invention
The present invention relates to computer peripheral processes and devices, such as a printer, facsimile machine or copier, providing image scanning functions and, more particularly, to processes and devices for detecting the leading edge of a sheet of printable medium (e.g., paper) in a computer peripheral device.
2. Discussion of Related Art
Along with recent trends in multimedia technology, common computer peripheral devices such as printers, have begun to incorporate scanner functions to complement desktop computer systems. In all such multi-function peripherals, a sheet of printable medium such as cut sheets of paper must be fed into the peripherals, and the leading edge of the sheet must be detected in order to determine the position of the sheet of paper in order to initiate the desired function, that is, either printing work, scanning work, or other task of image formation. Typically, a paper detection sensor is conventionally employed to sense the presence of the leading edge of the sheet, and an information signal is generated by the sensor to relay an indication of the detection. The information signal is applied as an electrical signal to a central processing unit (CPU), and the central processing unit generates a control signal to drive a line feed motor.
I have noticed that in such desktop systems, the central processing unit requires a dedicated input/output port to accommodate detection of the paper detection signal; this increases product cost and lowers the efficiency of the processor. I have also found that as paper detection sensors have proven to be inherently failure prone, there is the additional problem of reduced reliability and the concomitant inconvenience of replacement and repair of the system.